Resistance-box.



Patented Oct; 24, I899.

no. 635,44I.

H. W. LEONARD.

RESISTANCE BOX.

'(Applicafiion filed Nov. 3, 1898.)

(No Model.)

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FFTUEQ HARRY \VARD LEONARD, OF NE\V YORK, N. 'Y.

RESISTANCE-X.

SPECIFIGATION forming part of Letters Patent No. 635A41, dated October 24, 1899.

Application filed November 3, 1898. $crial No. 695,370. (N0 model.)

To aZZ whom it may concern.-

Be it known that l, HARRY WARD LEONARD, a citizen of the United States, residing in the borough of Manhattan, city of New York, county and State of New York, have invented a certain new and useful Improvement in Resistance-BoXe-s, of which the following is a specification.

My invention relates to improvements in resistance-boxes and similar apparatus, and especially to resistance-boxes employed for starting and accelerating electric motors.

The object of my invention is to make the apparatus as a whole more compact, simpler and cheaper to manufacture than heretofore, more durable and better adapted to the uses for which the apparatus is designed, and to enable the apparatus when damaged to be more readily and more cheaply repaired than was heretofore possible.

In carrying my invention into effect I prefer to employ a resistance made in the form of a ribbon and preferably reflexed or otherwise bent into shape, so that a considerable length of resistance maybe disposed in a comparatively small space. For the resistance material I preferably employ a metal or alloy having a high fusing-point and low-tempera ture coefficient for change of resistance by change of temperature. This resistance I arrange Within a shallow metal box, preferably cast-iron, and which is covered on the inner side with a layer of insulation, either by providing the same with a layer of asbestos or equivalent heat-resisting insulating material or by coating the same with an insulating compound capable of withstanding a high heat; but I prefer to apply a layer of porcelain enamel. When the resistance is placed in position within the box and connected with the usual binding-posts, I fill the box with sand or equivalent material, preferably sand. This sand is preferably a pure grade of sand, such as Berkshire sand, having a high capacity for heat absorption and possessing high insulating properties and one which is not readily affected by moisture or heat. The .sand being quite fine it readily fills all spaces within the boX between and around the sections of the resistance and at tached parts, and thus effectively insulates all parts of the apparatus located within the box. The box is closed by a metal lid having its inner side covered with insulation in the same manner as the box, and before placing the lid in position its edges or the edges of the boX receive a layer of sealing materialsuch, for instance, as puttyso that when the cover is secured in position, either by screws or otherwise, the box is well sealed, thus preventing the entrance of moisture and preventing the sand from working out. Since the resistance is secured only to the terminals or binding-posts for the steps or sections of the resistance, it will be seen that the loops between such binding-posts embedded in the sand or equivalent material will be entirely free to expand and contract wit-h the changes in temperature without producing any inj urious strains, as is the casein the constructions in which the resistance is secured directly to its support. Another advantage is that in completing the resistance-box the parts are not subjected to heat, as in the constructions just mentioned. It will thus be seen that the cost of manufacture of the apparatus thus outlined is very low, that the parts are readily and quickly placed in position, and that the apparatus may be readily taken apart for alteration or repair. Furthermore, the apparatus is very strong and compact, and the castiron box filled with sand has a very high capacity for absorbing heat energy because of the high specific capacity of the iron and sand for heat. The porcelain-enamel lining gives an insulation on the surface of the iron which is extremely perfect and not affected by heat, moisture, or any conditions met within practice, and such a coating can be readily made to withstand a pressure of many thou sand volts alternating electromotive force without injuring its insulating quality. The sand insulation between and around the parts located in the box is not readily affected by heat even though the temperature of the conductor reaches the melting-point.

It will be readily seen that should the apparatus become damaged-such, for instance, as the burning out of the resistance the apparatus may be readily repaired by first removing the cover and then removing the sand insulation and the burnedout resistance. hen a new step of resistance is put in position in place of the burned-out step, the

box is again filled with sand and the cover replaced, when the apparatus will be practically as good as when originally constructed, and practically the entire cost of repair in such a case would be represented by the cost of a new step of resistance, the cost of which is extremely low, being only a few cents.

I am aware that it has been heretofore proposed to construct resistance-boxes wherein the resistance was embedded in sand; but so far as I am aware no one prior to my invention has produced a practical resistance-box of the character described. The box itself should be moisture-proof far as practicable to prevent the sand from absorbing moisture, and I have found by experiment that the metal box must be lined with insulation not only to guard against a short circuit between the box and resistance due to moisture, but to guard against accidental contact between the box and resistance. 1 have also found that if any water be present in the box, either combined, as in cement, or otherwise, the heating of the conductor and sand when the resistance-box is in use will cause the moisture to collect on the inner side of the metal box, and unless the layer of insulation were provided on the inner side of the box a ground would soon be formed between it and the resistance.

I have found in practice that as a starting resistance for a twenty-live-horse-power mo tor a resistance-box constructed in accordance with my invention and provided with a resistance of the proper capacity the size of the box need not be over fourteen by fourteen by one and one-half inches. For such motors resistance boxes as heretofore constructed and in which the resistance was composed of coils of galvanized or tinned ironware were many times larger than the size above stated and very expensive and the resistance could not be so well protected as with my improved apparatus.

In making resistances for large motors such, for example, as three-hundred-horse power1 prefer to employ a series of resistance-boxes of about the size stated, the boxes, or rather the resistances of each box, being arranged in multiple with relation to each other. Such boxes would be secured together so as to form a bank of resistances, connections of course being made with a suitable controller. B i this means a standard form of resistance-box may be employed for 1110 tors operating on circuits of given voltagesthat is to say, one standard box would be for a twenty-five-horse-power motor employed on one-hundred-and-twonty-iive-volt circuits, another standard box for a twenty-iive-horsepower motor operating on two-hundred-an lfifty-volt circuits, and a third standard box for a twenty-five-horsepower motor operating on five-hundred-volt circuits, and by grouping resistanceboxes of the samestandard in banks resistances may be readily made up for motors varying from twenty-ii ve-horse power up and operating on circuits of one hundred and twenty-five, two hundred and fifty, or five hundred volts. Thus it will be seen that only three types of resistance-boxes would be necessary for all customary uses, and each of the three types would be alike in all respects, except as regards the capacity of the resistance-ribbon. Thus it will be seen that the manufacture of resistance-boxes may be very much simplified by means of my invention and the cost materially reduced on that account. The boxes will be of uniform size, but for the three types of motors mentioned the resistances will vary. \Vith boxes and resistances in stock resistanceboxes of any capacity can be made up in a very short time by means of my invention. All that is necessary is to select the necessary number of resistances of proper capacity, place them in the boxes, fill the boxes with sand, and apply the covers. 4

My invention is illustrated in the accompanying drawings, in which- Figure l is a plan view of the preferred form of my improved resistance-box, the lid being removed. Fig. 2 is a cross-soction, and Fig. 23 an elevation illustrating a bank of re sistanceboxes.

Referring to the drawings, A is the castiron box, which may be made in any desired form and is provided with a lid or cover 13, adapted to be secured to the box by any suitable means. lhe box and lid are respectively provided with ribs a and Z) for increasing the heat-radiating surface. The inner sides of the box and lid are covered with a layer of insulating material C capable of withstanding high heat, which, as before stated, may be asbestos or other insulating material, or the insulation may be an insulating compound applied in a liquid or semiliquid form, but it is preferably a coating of porcelain enamel. The resistance-box is provided with a series of binding-posts D, projecting through one side of the box or through the bottom (both ways being shown) and preferablyinsulated by bushings (l and wash ers tZ,of any suitable insulating material. These binding-posts are held in position by nuts (1 and at the outer ends are provided nuts (Z for securing the circuit-terminals. The sections of the resistance E are secured to clamps c, which in turn are secured to the binding-posts between the washer d and a metal washer d". As before stated, the resistance is in the form of a thin ribbon, and this ribbon is preferably reflexed, as shown, and placed edgewise in the box. As a precautionary measure a strip of insulating material F may be placed edgewise between the adjacent sections of the resistance, as shown in dotted lines, although in practice I have found that it is not absolutely necessary. \Vhen the resistance E is placed in position and the sections secured to the binding-posts D, as described, the box is filled with a fine sand G. Before placing the cover in position TIO I apply to the edge of the box or cover a layer of sealing material bsueh, for instance, as putty, although any suitable material may be employed-and the cwer is then firmly securedin position by screws passing through the cover into the sides of the box or otherwise. To improve the joint between the box and cover, I provide the edge of the box with a groove a to retain the sealing material. Each box is also provided with four legs or studs A, one at each corner of the box, and through each leg or stud is formed a hole A to receive a screw for securing the box in position. The studs A and holes A are also designed for use in arranging the resistanceboxes in banks, as shown in Fig. 3', the studs, with additional pieces of tubing, serving as spacing-blocks, and through the holes A are passed rods by means of which the several boxes are clamped together and secured to a suitable base or supporting-stand.

What I claim is- 1. In a resistance-box, the combination of a metal box, a resistance in the box, a finelydivided mineral insulating filling material in said box, and a cover for said box having sealed joints.

2. In a resistance-box, the combination of a metal box, an insulatinglining for such box, a resistance in the box, a finely-divided mineral insulating filling material in said box, and a cover for said box having sealed joints.

3. In a resistance-box, the combination of a metal box, a heat-resisting insulating-lining for such box, a resistance in. the box, a finelydivided mineral insulating filling material in said box, and a cover for said box having sealed joints.

4. In a resistance-box, the combination of a metal box, a porcelain-enamel insulatinglining for such box, a resistance in the box, a finely-divided mineral insulating filling material in said box, and a cover for said box having sealed joint-s.

5. In a resistance-box, the combination of ametal box, an insulating-lining for such box, a reflexed resistance in the box, insulatingpartitions between adjacent sections of the resistance, and a mineral insulating filling material in said box.

6. In a resistance-box, the combination of a metal box, a heat-resisting insulating-lining forsucha box, a reflexed resistance in the box, insulating-partitions between adjacent sections of the resistance, a finely-divided mineral insulating filling material in said box, and a cover for said box having sealed joints.

7. In a resistance-box, the combination of a metal box, a porcelain-enamel insulatinglining for such. box, a reflexed resistance in the box, insulating-partitions between adjacent sections of the resistance,a finely-divided mineral insulating filling material in said box, and a cover for said box having sealed joints.

8. In a resistance-box, the combination of a metal box, a porcelain-enamel insulatinglining for such box, a resistance in the form of a tape or ribbon in the box, and a mineral insulating filling material in said box.

5). In a resistance-box, the combination of a metal box, an insulating-lining for such box, a resistance in the form of a tape or ribbon in the box, a finely-divided mineral insulating filling material in said box, and a cover for said box having sealed joints.

10. In a resistance-box, the combination of a metal box, a heat-resisting insulating-lining for such box, a resistance in the form of a tape or ribbon in the box, a finely-divided mineral insulating filling materialin said box, and a cover for said box having sealed joints.

11. In a resistance-box, the combination of a metal box, a porcelain-enamel insulating lining for such box, a resistance in the form of a tape or ribbon in the box, a finely-divided mineral insulating filling material in said box, and a cover for said box having sealed joints.

12. In a resistance-box, the combination of a metal box, a heat resisting insulating-lining for such box, a reflexed resistance in the form of a tape or ribbon in the box, insulating-partitions between adjacent sections of the resistance, a finely-divided mineral insulating filling material in said box, and a cover for said box having sealed joints.

13. In a resistance-box, the combination of a metal box, a resistance in the box, said resistance being arranged in steps connected with a series of insulated contacts or bindingposts, a finely-divided mineral insulating filling material in said box for insulating adjacent sections of the resistance from each other and for absorbing and conducting the heat from said resistance to the metal box, and a cover for said box having sealed joints.

lat. In a resistance-box, the combination of a metal box, aninsulating-liningforsuch box, a resistance in the box, said resistance being arranged in steps connected with a series of insulated contacts or bindingposts, a finelydivided mineral insulating filling material in said box for insulating adjacent sections of the resistance from each other and for absorbing and conducting the heat from said resistance to the metal box, and a cover for said box having sealed joints.

15. In a resistance-box, the combination of a metal box, a resistance in the box, said resistance being arranged in steps connected with a series of insulated contacts or bindingposts,said resistance being unattached to said box except where connected to said contacts or binding-posts, a finely-divided mineral insulating filling material in said box for insulating adjacent sections of the resistance from each other and for absorbingand conducting the heat from said resistance to the metal box, and a cover for said boxhaving sealed joints.

16. In a resistance-box, the combination of a metal box, an insulating-lining t'orsuch box, a resistance in the box, said resistance being arranged in steps connected with a series ot' insulated contacts or binding-posts, and said resistance being unattached to said box except where connected to said contacts or binding-posts, a finely-divided mineral insulating filling material in said box for insulating adjacent sections of the resistance from each other and for absorbing and conducting the heat from said resistance to the metal box, and a cover for said box having sealed joints.

17. In a resistance-box, the combination of a metal box, a porcelain-enamel insulatinglining for such box, a resistance in the box, said resistance being arranged in steps connected with a series of insulated contacts or binding-posts,and said resistance being unattached to said box except where connected to said contacts or bindingposts,a finely-divided mineral insulating filling material in said box for insulating adjacent sections of the resistance from each other and for absorbing and conducting the heat from said resistance to the metal box, and a cover for said box having sealed joints.

18. In a resistance-box, the combination of a metalbox, an insulating-lining for such box, a resistance in the form of a tape or ribbon in the box, said resistance being'arranged in steps connected with a series of insulated contacts or binding-posts, and said resistance being unattached to said box except where connected to said contacts or binding-posts, a finely-divided mineral insulating filling material in said box for insulating adjacent sec tions of the resistance from each other and for absorbing and conducting the heat from said resistance to the metal box, and a cover for said box having sealed joints.

19. In a resistance-box, the combination of a metal box, a porcelain-enamel insulating-lining for such box, a resistance in the form of a tape or ribbon in the box, said resistance being arrangedin steps connected with a series of insulated contacts or binding-posts, and said resistance being unattached to said box except where connected to said contacts or binding-posts, a finely-divided mineral insulating filling material in said box for insulating adjacent sections of the resistance from each other and for absorbing and conducting the heat from said resistance to the metal box, and a cover forsaid box having sealed joints.

20. In a resistance-box, the combination of a shallowbox, a resistance within said box arranged in steps or sections, terminals to which said steps or sections are conneeted,-a finely divided insulating filling material surrounding said resistance, and a removable cover for said box having sealed joints.

21. In a resistance-box, the combination of a shallow metal box, a resistance within said box arranged in steps or sections, terminals to which said steps or sections are connected, a finely-divided insulating filling material surrounding said resistance, and a removable cover for said box having sealed joints.

22. In a resistance-box, the combination of a shallow metal box having an insulating lining, a resistance within said box arranged in steps or sections, terminals to which said steps or sections are connected, a finely-divided insulating filling material surrounding said resistance, and a removable cover for said box having sealed joints.

23. In a resistance-box, the combination of a box having two large parallel surfaces and a relatively narrowedge, one of the large surfaces being in the form of a cover, a resistance within the box arranged in steps or sections, terminals to which said steps or sections are connected, and a removable filling of mineral insulating material surrounding said resistance.

24. In a resistance-box, the combination of a cast-iron box having two large parallel surfaces and a relatively narrow edge, one of the large surfaces beingin the form of a cover, a resistance within the box arrangedin steps or sections, terminals to which said steps or sections are connected, and a removable filling of mineral insulating material surrounding said resistance.

25. In a resistance-box, the combination of a box having two large parallel surfaces and a relatively narrow edge, one of the large surfaces being in the form of a cover, a resistance in the form of a tape or ribbon placed edgewise in the box and arranged in steps or sections, terminals to which said steps or sections are connected, and a removable filling of mineral insulating material surrounding said resistance.

26. In a resistance-box, the combination of a box having two large parallel surfaces and a relatively narrow edge, one of the large surfaces being in the form of a cover having sealed joints, a resistance in the box and arranged in steps or sections, terminals to which said steps or sections are connected, and a finely-divided insulating filling material surrounding said resistance.

27. In a resistance-box, the combination of a box having two large parallel surfaces and a relatively narrow edge, one of the large surfaces being in the form of a cover having sealed joints, a resistance in the form of a tape or ribbon placed edgewise in the box and arranged in steps or sections, terminals to which said steps or sections are connected, and a finely-divided insulating filling material surrounding said resistance.

28. In a resistance-box, the combination of a cast-iron box having two large parallel surfaces and a relatively narrow edge, one of the large surfaces being in the form of a cover having sealed joints, a lining of insulation, a resistance in the box and arranged in steps or sections, terminals to which said steps or sections are connected, and a finely-divided insulating filling material surrounding said resistance.

This specification signed and witnessed this 20th day of October, 1898.

H. IVARD LEONARD. \Vitnesses:

O. E. CARPENTER, W. H. MoOnnsNnY. 

